Gasoline upgrading

ABSTRACT

A combination processing arrangement of reforming, isomerization, aromatics recovery and intervening fractionation is described which will improve upon the yield of gasoline product having a lead free octane rating above 90 by particularly upgrading C6 hydrocarbons.

United States Patent [151 3,658,690 Graven [4 1 Apr. 25, 1972 [54]GASOLINE UPGRADING 3,280,022 10/1966 Engeletal. ..208/63 3,001,9279/1961 GerholdetaL. ...208/64 [72] Inventor: Richard G. Graven,Westmont, NJ. 3,121,676 2/l964 Skraba "Jog/62 [73] Assignee: Mobil OilCorporation, New York, NY, 2,965,561 12/1960 Carr et al ..208/65 [22]Filed: Mar. 13, 1970 I FOREIGN PATENTS OR APPLlCATlONS [21] App]. No.:19,377 248,938 12/1960 Australia ..208/62 Primary Examiner-HerbertLevine [52] U.S. Cl ..208/62, 208/63, 208/79: Atmmey OSwald Hayes,Andrew L Gaboriault and Car] 208/92* 208/93 D. Famsworth [51] Int. Cl..ClOg 39/00 [58] Field of Search ..208/62-66, 80, 57 ABSTRACT Acombination processing arrangement of reforming, isome- R C-tedrization, aromatics recovery and intervening fractionation is [56] eerences I described which will improve upon the yield of gasoline UNITEDS TES T NTS product having a lead free octane rating above 90 byparticularly upgrading C hydrocarbons. 2,905,619 9/l959 Sutherland..208/64 3,165,461 1/1965 Wade et a1 ..208/64 4 Claims, 1 Drawing Figure26 32 Deisopentonizer lsomerizotion 3a ZZDMB l0 Aromatic 2 4 5Separation Hyd'ogemho" 50 Aromcnics 42 Depenfonizer ReformoteDehexonizer GASOLINE UPGRADING BACKGROUND OF THE INVENTION The need forproviding lead-free gasoline products to accommodate gasoline combustionengines employing regular and high test leaded gasoline has beenprompted by the need to reduce air pollution problems confronting areasof high automobile density. Thus it is predictable that major airpollution reductions can be realized particularly in areas of highantomobile density by eliminating lead additive to regular and highoctane gasoline. Recent press releases have emphasized the need for suchcontrols and in fact plans are in progress to grant the Secretary ofHealth, Education and Welfare, authority to set standards of compositionof fuel which includes the removal of lead from gasoline. Thus thepresent invention is concerned with a processing arrangement or sequenceone might now employ in present refinery arrangements with a minimum ofadditional investment to upgrade low octane gasoline material unsuitablefor use in present gasoline combustion engines to an acceptable unleadedhigher octane product suitable for use in the combination engine as weknow it now and changes recommended with respect thereto in theimmediate future. In some instances it has been recommended that thecompression ratio of today's engines by reduced so that they will bemore compatable for operating on gasoline products having an octanerating'clear in the range of 90 to 100 octane. Some prior art patents ofinterest in upgrading gasoline are US. Pat. Nos. 2,905,619, 3,165,461and 1,900,323.

SUMMARY OF THE INVENTION The present invention is directed to aprocessing arrangement for upgrading gasoline boiling range material ofunsatisfactory octane rating to a higher octane gasoline productsuitable for use in gasoline combustion engines without lead additives.In a particular aspect the present invention is directed to thecombination of processing steps comprising hydrogenation, reforming,aromatic extraction and C hydrocarbon isomerization as they relate toone another in the combination for upgrading low octane constituents ofthe gasoline charge to acceptable higher octane product. One importantaspect of the processing combination of this invention relates toupgrading low octane C hydrocarbon components.

BRIEF DESCRIPTION OF THE DRAWING The drawing diagrammatically presentsone arrangement of processing steps for upgrading gasoline materialboiling from about C hydrocarbons up to about 380 F. by a processingcombination which includes reforming, isomerization, aromatic recoveryand intervening separation steps designed to concentrate desired octaneconstituents from undesired gasoline component of low octane ratingwhich are convertable to higher octane blending components.

DESCRIPTION OF A SPECIFIC EMBODIMENT THe present invention is concernedwith a processing arrangement which may be utilized in present dayrefinery operations to upgrade low octane gasoline material andparticularly C components thereof to a much higher octane productsuitable for blending with reformed gasoline product of a desired higheroctane rating. More particularly the processing arrangement identifiedby this invention upgrades particularly C and higher boilinghydrocarbons in the gasoline boiling range by the operating arrangementof reforming, isomerization, aromatic recovery with interveningstabilization and fractionation designed to particularly upgrade, withmuch greater emphasis, the low octane C hydrocarbon components. In thespecific processing scheme shown by the drawing, a relatively low octanegasoline boiling charge such as defined below and having an initialboiling point of about C hydrocarbons and an end boiling point of about380 F. is introduced to the process by line 2 for passage tohydrogenation pretreater 4 such as desulfurization. In pretreater 4 thegasoline charge is subjected to hydrogenation conditions which will beeffective for removing sulfur and nitrogen components found in thegasoline charge. The amount of sulfur and nitrogen components in thecharge will vary considerably depending upon the source of the gasolinecharge. That is, the gasoline charge may be either a straight runnaphtha, coker gasoline, gasoline product of hydrocracking or catalyticcracking, and/or mixtures thereof. The hydrogenated charge is thereafterstabilized as by fractionation to remove undesired low boilingconstituents. The stabilized charge is passed by line 6 to adepentanizer tower 8. The depentanizer tower 8 is maintained underoperating conditions particularly selective to separate C and lowerboiling hydrocarbons from a higher boiling hydrocarbon fractioncomprising C and higher boiling hydrocarbons. The C and lower boilinghydrocarbons are removed from the upper portion of tower 8 by line 10.The C and higher boiling hydrocarbons having, for example, thecomposition of C and higher boiling gasoline hydrocarbons are withdrawnfrom the bottom of depentanizer tower 8 by line 12. It is to beunderstood that the separation effected in depentanizer tower 8 isdesigned to carry substantially all of the C and higher boilinghydrocarbons into the bottom phase and thus it is expected that some Chydrocarbons will be carried along therewith. However, the bottomfraction in line 12 is primarily C and higher boiling hydrocarbonscomprising the higher boiling components of the gasoline fractionboiling up to about 380 F. Desulfurization of the gasoline boilingcharge may be effected after passing through the depentanizer ratherthan before. The thus obtained depentanized charge is passed by line 12to a platinum reforming operation in zone 14 wherein the reformingseverity conditions are selected to provide reformate product varyingconsiderably in octane rating. Depending on conditions employed andreformate cut point, it may have a relatively high octane rating as highas about 104 or 106 octane numbers clear or it may be considerably lowerand as low as octane clear basis. The reforming operation effected inzone 14 relies upon a platinum-type reforming catalyst provided withsuitable catalyst promoters to achieve the results desired. Although notspecifically shown it is to be understood that a typical reformingoperation known in the prior art and comprising three or more reactorswith separation equipment so that the effluent obtained from reformingwill pass through one or more separation zones to stabilize thereformate product and effect the recovery of normally gaseous componentsrich in hydrogen from a higher boiling reformate product containing Cand higher boiling hydrocarbons. The separated normal gaseous componentsnot shown in the drawing and comprising a hydrogen rich recycle gas maybe recycled to the reformer or used in another suitable portion of theprocessing sequence herein discussed. The reformate product obtainedfrom reforming zone 14 and comprising primarily C and higher boilinghydrocarbons is then passed by line 16 to a depentanizer tower 18.Depentanizer tower 18 is maintained under conditions designed to permitseparation and recovery of primarily C and higher boiling hydrocarbonshaving the characteristics identified in Table 1. This C and higherboiling reformate fraction is withdrawn from the bottom portion of thetower by line 20 with primarily C hydrocarbon components and any lowerboiling material being withdrawn from the upper portion of the tower byline 22.

TABLE 1 PtR Yields and Reformate PONA (paraffins, olefins, naphthenesand aromatics) Composition for 350 psig Reforming of C -380F. TBP (totalboiling point) MCS (Mid-Continent Sour) Naphtha After Adjustment for a1.5% vol Loss in C Reformate Yield Recycle Gas Water Level OptimumOctane C R+3 104.0 C R+ 99.7 C,,+. R+3 105.1 C,+, R+O 101.7 Yields VolWt Mol C5+ 73.6 78.7 86.7 C 8 7.9 6.6 10.2 C,S 8.6 6.6 12.8 DG 14.6150.6 11 1.8 102.3 C, 2.4 17.1 C, 4.0 15.0 C, 6.3 16.2 1C, 3.5 2.6 5.1NC, 5.1 4.0 7.7 1C, 4.9 4.1 6.4 NC 2.9 2.5 3.8 C 65.7 72.2 76.4 Total82.21 100.0 250.0 H,S Cf/Bbl 906. C,+ Reformate Properties Sp. Gr.0.8021 M01. Wt. 102.0 RVP (reed vapor pressure) 3.79 Recycle GasComposition H: 71.1 C 1 1.3 C, 8.1 C, 5.8 1C 1%] NC 1.3 1C, 0.5 NC, 0.3[C 0.2 NC 0.1 C, 0.1 C 0.3 M01. Wt. 10.8 Sp. Gr. 0.3716 C,,+ Yields VolWt Mol Paraffins 18.5 16.7 19.9 Olefins 1.0 0.9 1.3 Naphthenes 0.5 0.50.7

Aromatics 45.7 54.0 54.6 a 9.3 8.2 10.7 C P 6.9 6.4 7.1 C,,P 2.2 2.1 2.1C,+ P 0.0 0.0 0.0 Benzene 3.0 3.5 5.1 Toluene 13.2 15.3 18.7 C Aromatics14.6 16.9 17.9 09+ Aromatics 14.9 18.2 12.9

The C and lower boiling hydrocarbonsrecovered from depentanizers 8 and18 are combined and passed to a debutanizer tower 24 wherein C and lowerboiling hydrocarbons are separated from C hydrocarbons. The C and lowerboiling hydrocarbons are withdrawn from debutanizer tower 24 by line 26.The C hydrocarbon rich stream comprising about 50.4% n-C hydrocarbonsare passed by line 28 to deisopentanizer tower 30. In deisopentanizertower 30, a separation is made between normal pentane and isopentane sothat a 95 percent rich isopentane stream may be withdrawn from the upperportion of the tower by line 32. Normal pentane is recovered from thebottom of tower 30 and passed by line 34 to an isomerization zone 36.lsomerization zone 36 is relied upon to convert normal pentane toisopentane and the product obtained therefrom is passed todeisopentanizer tower 30 by way of line 38 and 28. The isomerization ofpentanes is well known in the art and known catalyst compositions andoperating conditions may be employed to effect such an isomerization. Itis intended that any of the well known and reliable isomerizationprocesses be employed and particularly one which will economicallyconvert normal pentane to isopentane. The product obtained fromisomerizing step 36 is passed to tower 30 by line 38 for effectingseparation of normal from isopentane. The recovered isopentane in line32 may then be employed as blending stock in gasoline product or usedfor other purposes known in the art.

The reforming effluent recovered from the bottom of depentanizer tower18 and having the composition identified in Table 1 above is thereafterpassed by line 20 to dehexanizer tower 40 wherein the operatingconditions are maintained to effect a separation between a hydrocarbonfraction boiling in the range of from about C hydrocarbons up to a cutpoint in the range of from about F. to 225 F. from a reformate fractionboiling above the cut point selected and comprising the high octanegasoline reformate product of reforming zone 14.

It is known that the product of platinum reforming contains some verylow octane components comprising C and C hydrocarbons which can bereadily separated by distillation. These low octane materials areprimarily C and C paraffins which have not been converted duringreforming as by dehydrogenation, aromatization, isomerization andhydrocracking. Thus reformate splitting in dehexanizer tower 40 permitsone to adjust the octane rating and yield of the product obtained asillustrated by the Table below.

Reformer Charge C 380 F. MCS

Reformer pressure 350 psig Start-of-cycle Conditions Reformer Severity,C,

The light hydrocarbon fractions resulting from reformate splitting, assuggested above, may be upgraded by processes such as hexaneisomerization, shape selective processing and alkylation afterconversion to suitable olefins, or disposed of as fuel. The octanenumber of these light fractions are represented below.

Reformer Charge C 380 F. MCS

Reformer Pressure 350 psig.

Start-of-cycle Conditions Reformer Severity, C

+ R+3 cc TEL 106 108 C 158F Fraction Estimated Yield, 7: vol of RRCharge 9.6 7.1 4.0 Estimated Octane Number, R+0 68.3 69.1 71.8 C,,200F.Fraction Estimated Yield, vol of PtR Charge 18.2 13.8 9.0 EstimatedOctane Number, R+0 75.3 79.2 86.7

The relatively high octane reformate product obtained, as

1n the processing arrangement of this invention the hydrocarbon fractionin line 44 is first treated to remove aromatics therefrom and Chydrocarbons. Since it is known that aromatics in an isomerizationcharge have an undesirable in- I fluence upon the isomerizationreaction, the aromatics are removed such as by liquid phase extraction,molecular sieve adsorption techniques or any other available means forac complishing the same. The aromatics thus recovered are removed byline 48 for use as desired. In some instances they may be combined withthe gasoline product or used in the chemical industry. The aromatics maybe separately recovered through line 50.

The aromatic freed hydrocarbon fraction comprising C hydrocarbons andpossibly some C hydrocarbons is thereafter passed to tower 47 providedto effect separation of C hydrocarbons which are withdrawn from thebottom of the tower. The remaining C hydrocarbon stream is then passedby line 52 to hydrogenation step 54 wherein the conditions employed aresuch as to hydrogenate any aromatics remaining in the charge after thetreatment just discussed. The hydrogenated product freed of aromaticsand difficulty isomerizable C hydrocarbons is then passed by line 56 toisomerization zone 58. In the isomerization zone 58 the conditions ofoperation such as low temperatures are selected which will be effectivein producing 2,2-dimethylbutane. The products of isomerization obtainedin zone 58 are then passed by line 60 to a separator tower 62 whereinseparation is made, for example, to recover 2,2-dimethylbutane alongwith some 2,3- dimethylbutane from the upper portion of the tower byline 64. Higher boiling material is withdrawn from the bottom portion ofthe tower by line 66 for passage, all or in part, to platinum reformingor recycle by line 68 to isomerization step 58. Care must be taken toavoid build-up of naphthenes as by recycle in the charge to theisomerization zone 58 and thus conversion of this material as byplatinum reforming, thermal and catalytic cracking and olefinic productthereof by alkylation is contemplated. v

It is clear from the above discussion that the novel process arrangementof the present invention selectively separates and upgrades low octanecomponents into acceptable higher octane products. Thus by separatingout low octane C and C components and separately upgrading them toacceptable octane product under essentially more optimum conversionconditions, substantially improved yield results are also obtained andthese improved results permit increased yield of regular as well aspremium grade gasoline product.

The combination of reforming and isomerization discussed herein isrelied upon to upgrade the gasoline charge comprising C and higherboiling hydrocarbons. The reforming opera- -tion, either a regenerativetype such aspowerforming or a semiregenerative type is effected in aplurality of reactors suitably connected as known in the prior art at atemperature in the range of from about 700 F up to about l,050 F. toeffeet the known reforming reactions of dehydrogenation,

cyclization, aromatization, isomerization and some limited cracking .ofthe charge. The reforming operation may be effected at a'pressure in therange offrom about 100 psig up to about 1,000'psig, it'being preferredto employ as low a pressure as possible to achieve the results desired.Generally the pressure will not be significantly above 500 psig and moreusually the pressure will-be below about 350 or 400 psig. A liquidhourly space velocity selected from within the range of 0.5 up to aboutmay be employed in the presence of hydrogen in a mol ratio withhydrocarbon in the range of 0.5 up to about 20. The reforming catalystsemployed are usually Group Vlll metals of the platinum type dispersed ona suitable carrier material such as alumina in the eta, gamma or mixedeta-gamma form. The platinum hydrogenation-dehydrogenation component maybe used alone or in combination with other metal promoters known in theart. The amount of platinum used varies in the range of from about 0.01percent up to as high as about 2 or 3 percent, it being preferred to useless than about 1 percent in most cases. The reforming catalyst maycontain a halogen promoter and is usually of a particle form sizesuitable for use in a fixed bed reforming operation.

The isomerization of either C or C hydrocarbons may be efiected withsolid type isomerization catalyst rather than the more corrosive liquidisomerization catalysts. A solid type of reforming catalyst may compriseplatinum disposed on alumina and promoted with an acidic agent such ashalogen or boron. Low temperatures are particularly desirable in theisomerization reactions. The production of neohexane by aluminumchloride isomerization at temperatures above and below about 200 F. isknown. Furthermore isomerizing with the solid type of isomerizationcatalyst at temperatures in the range of from about 200 F. up to about800 F. may be employed with low temperatures in the range of 200 F. toabout 350 F. preferred. Of course the various isomerization catalystsare not necessarily equivalent and operating conditions employed will betailored to the specific catalyst em ployed. The isomerizing pressuremay be selected from within the range of 50 psig up to about 1,000 psigbut is preferably selected from within the range of l00 to about 500psig. Regardless of the particular isomerization process employed, theoperating conditions will be selected so that a selective operation ispursued which minimizes cracking and other undesired side reactions.Therefore, in the interest of optimizing the selectivity of the presentoperation, normal pentanes are separately isomerized from the normalhexanes. The isomerization of pentanes and hexanes is discussed in theliterature and the method of the present invention intends to rely uponthis information to its maximum advantage.

The removal of aromatics from the C hydrocarbons isolated by the methodof the present invention is particularly important since such aromaticsin the charge to isomerization are known to be most undesirable.Furthermore, C hydrocarbons are isomerized only with extreme difficultyand their removal from the C hydrocarbon charge to be isomerized is alsomost desirable. The removal of aromatics such as benzene and toluene maybe accomplished by extraction, molecular sieve adsorption or any otherknown available method. Thereafter C hydrocarbons may be removed fromnormal C hydrocarbons by fractionation carefully controlled.

Having thus provided a general description of the present invention andpresented a specific example in support thereof, it is to be understoodthat no undue restrictions are to be imposed by reason thereof except asdefined by the following claims.

I claim:

1. A combination process for upgrading gasoline boiling range materialobtained as straight run naphtha, coker gasoline, gasoline product ofhydrocracking and catalytic cracking and mixtures thereof whichcomprises:

a. separating said gasoline boiling range material under conditions torecover a first hydrocarbon fraction consisting essentially of C andlower boiling hydrocarbons from a higher boiling fraction consistingessentially of 'C and higher boiling hydrocarbons,

b. reforming said higher boiling fraction and recovering a secondhydrocarbon stream rich in C hydrocarbons from a higher boilingreformate product stream,

c. combining said hydrocarbon streams containing C hydrocarbons andisomerizing the normal pentane components therein,

d. separating the higher boiling reformate product stream at a cut pointin the range of from about l50 F. up to about 225 F. to obtain a lowboiling stream thereof rich in C hydrocarbons from a higher boilingreformate product fraction of acceptable octane rating suitable for usein regular or premium unleaded gasoline,

e. removing aromatics and any entrained C hydrocarbons from said C richhydrocarbon stream,

f. isomerizing said rich C hydrocarbon stream from step (e) underconditions selected to produce significant quantities of C isomers andg. recovering C isomers as blending components for use in regular andpremium gasoline.

2. The method of claim 1 wherein said gasoline boiling range material isdesulfurized before effecting separation thereof.

3. The method of claim 1 wherein desulfurization of the fractions isaccomplished after the separation of step (a).

4. The method of claim 1 wherein C hydrocarbons removed in step (e) areconverted to useful product materials by thermal and catalytic cracking.

@3 3 UNITED STATES LDATENT OFFICE CERTIFICATE @F CORRECTEON Patent No.3,658,690 Dated May 12, 1972 lnvent fl RICHARD G. GRAVEN It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 1, line 27 "by" should be --be-- Column 1, line 31 1,900,323"should be Signed and sealed this 3rd day of October 1972.

(SEAL) Attesc:

EDWARD MQFLETCHERJR. 7 ROBERT GOTTSCHALK Commissioner of PatentsAttesting Officer

2. The method of claim 1 wherein said gasoline boiling range material isdesulfurized before effecting separation thereof.
 3. The method of claim1 wherein desulfurization of the fractions is accomplished after theseparation of step (a).
 4. The method of claim 1 wherein C7 hydrocarbonsremoved in step (e) are converted to useful product materials by thermaland catalytic cracking.